Fossilised TREE FERN: Detail of mineralised cell structures

Bruce Williams · Post by **Bruce Williams** » Sun Mar 18, 2007 4:46 pm

Hi folks,

This is a follow up posting to the 2 images posted in the Macro/Close-up Forum yesterday: Section through 270 million year old fossilised tree fern. I recommend you take a look at that posting as it will provide useful context for the images in this posting.

This fossilised tree fern comes from the Maranhao Sedimentary Basin in NE Brazil. It grew in the Permian period (late Palaozoic era) approximately 270 million years ago. Species is almost certainly Tietea singularis.

This particular slice probably comes from near the base of the trunk/branch as it is almost entirely made of the central (supporting) stele. This is identifiable by the numerous brain-like structures of the vascular bundles of xylem tissue.

It's striking just how different the internal structure is from that of a tree.

The cellular detail was not visible in the Minolta A2 close-up shots so
I was really taken by surprise at finding so much detail still preserved at a microscopic level after more than 1/4 of a billion years!

Bruce

All images taken with Olympus SP-350 through Meiji EMZ-5TR. All CombineZM stacks of ~6 frames.

Ken Ramos · Post by **Ken Ramos** » Sun Mar 18, 2007 4:55 pm

Supurb!

There is a lot of microscopic detail to be seen after a quarter billion years there Bruce. It seems, if I am not mistaken, some on the cellular level too. These are fantastic, especially the second image. Very nice work, thanks

Wolfgang Bettighofer · Mon Mar 19, 2007 5:34 am

Hi Bruce,

thanks for the interesting insights! Can you tell something about preparation?

Wolfgang

Bruce Williams · Post by **Bruce Williams** » Mon Mar 19, 2007 10:49 am

Hi Wolfgang,

The photos were taken from a complete section of a fossilised tree fern, including bark (see posting in Macro/Close-Up Forum). It measures approximately 80mm in "diameter" and is about 6mm thick. Like fossilised wood all the original organic material has been replaced with minerals, mostly a form of quartz. the various colours are the result of impurities such as iron oxides (red) and manganese (orange and black). In this case a reasonable amount of microscopic detail has been preserved during the fossilisation process - this is not always the case.

In this instance examination is obviously only possible by reflected light. I have not come across sections of fossilised fern that are thin enough to view by transmitted light, but I'm sure they must exist. The equipment required to prepare the specimen so that maximum detail is visible is very large, very specialised and very expensive too.

The section is cut from the log using a very fine diamond tipped saw (typically 24" or 36" in diameter). The blade is continually lubricated with oil as the section is being cut - my guess is that it would have taken about 10 minutes to cut my piece.

The next stage is lapping and polishing to first create a optically smooth surface and then polish it to a high gloss sheen. This is an iterative process using progressively finer grades of diamond or ceramic powder and can take a considerable time (days sometimes) to complete depending upon the hardness of the mineral quartz and other inclusions. The larger the lapping plate the better (typically 2 to 3 feet in diameter).

All this requires a considerable amount of experience and skill to get it right as every log (wood, palm or tree fern) is different and requires careful management to avoid fracturing or fragmentation during the cutting stage and to judge the appropriate abrasive grit grades and timings of each stage in the lapping process.

Sadly I do not have these skills or the equipment (or the space to house it in) so must buy my pieces from others that possess both means and ability

I used a Meiji EMZ-5TR stereo microscope with duel fibre optic (halogen sourced) cold lights. Camera is an Olympus SP-350 with custom white balance, manual focus and CombineZM stacking of ~6 frames (in this instance). Post processing in Photoshop CS2.

Hope this helps.

Bruce

Wolfgang Bettighofer · Mon Mar 19, 2007 3:18 pm

Hi Bruce,

thank's for details. So I received an impression of perparation process and effort.

Wolfgang

beetleman · Post by **beetleman** » Mon Mar 19, 2007 3:51 pm

It IS amazing all the detail that is still left to see. Just fantastic Bruce.

Bruce Williams · Post by **Bruce Williams** » Sat Mar 24, 2007 2:36 am

Thanks for your encouraging comments guys.

Ken - Yes you're right, these images are definitely at the cellular level. I have another (less colourful) example from higher up the "trunk" that shows a greater range of cell types. I've not examined it thoroughly yet but I will be posting some pics for comparison purposes.

Doug - This was one of those rare but wonderful occasions when "reality" totally exceeded expectation

Bruce